de.schlichtherle.truezip.fs.nio.file.TempFilePool Maven / Gradle / Ivy

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/*
 * Copyright (C) 2005-2015 Schlichtherle IT Services.
 * All rights reserved. Use is subject to license terms.
 */
package de.schlichtherle.truezip.fs.nio.file;

import de.schlichtherle.truezip.socket.IOPool;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import static java.nio.file.Files.createDirectories;
import static java.nio.file.Files.deleteIfExists;
import static java.nio.file.Files.exists;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.FileAttribute;
import java.nio.file.attribute.PosixFilePermission;
import static java.nio.file.attribute.PosixFilePermission.GROUP_READ;
import static java.nio.file.attribute.PosixFilePermission.GROUP_WRITE;
import static java.nio.file.attribute.PosixFilePermission.OTHERS_READ;
import static java.nio.file.attribute.PosixFilePermission.OTHERS_WRITE;
import static java.nio.file.attribute.PosixFilePermission.OWNER_READ;
import static java.nio.file.attribute.PosixFilePermission.OWNER_WRITE;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.EnumSet;
import java.util.Set;
import javax.annotation.CheckForNull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.NotThreadSafe;
import javax.annotation.concurrent.ThreadSafe;

/**
 * This I/O pool creates and deletes temporary files as {@link FileEntry}s.
 *
 * @since  TrueZIP 7.2
 * @author Christian Schlichtherle
 */
@ThreadSafe
final class TempFilePool implements IOPool {

    private static final Path TEMP_DIR
            = Paths.get(System.getProperty("java.io.tmpdir"));

    private static final FileAttribute[] ATTRIBUTES = isPosix()
            ? posixAttributes()
            : emptyAttributes();

    private static boolean isPosix() {
        return FileSystems
            .getDefault()
            .supportedFileAttributeViews()
            .contains("posix");
    }

    private static FileAttribute[] posixAttributes() {
        return new FileAttribute[] { posixPermissions() };
    }

    private static FileAttribute[] emptyAttributes() {
        return new FileAttribute[0];
    }

    private static FileAttribute> posixPermissions() {
        return PosixFilePermissions.asFileAttribute(
                EnumSet.of(OWNER_READ, OWNER_WRITE,
                           GROUP_READ, GROUP_WRITE,
                           OTHERS_READ, OTHERS_WRITE));
    }

    /**
     * A default instance of this pool.
     * Use this if you don't have special requirements regarding the temp file
     * prefix, suffix or directory.
     */
    static final TempFilePool INSTANCE = new TempFilePool(null, null);

    private final @Nullable Path dir;
    private final String prefix;

    TempFilePool(
            final @CheckForNull Path dir,
            final @CheckForNull String prefix) {
        this.dir = null != dir ? dir : TEMP_DIR;
        this.prefix = null != prefix ? prefixPlusDot(prefix) : "tzp";
    }

    private static String prefixPlusDot(String prefix) {
        return prefix.endsWith(".") ? prefix : prefix + ".";
    }

    @Override
    public Buffer allocate() throws IOException {
        return new Buffer(createTempFile(), this);
    }

    private Path createTempFile() throws IOException {
        try {
            return Files.createTempFile(dir, prefix, null, attributes());
        } catch (final IOException ex) {
            if (exists(dir)) throw ex;
            createTempDir();
            return createTempFile();
        }
    }

    private static FileAttribute[] attributes() {
        return 0 == ATTRIBUTES.length ? ATTRIBUTES : ATTRIBUTES.clone();
    }

    private void createTempDir() {
        assert !exists(dir);
        try {
            createDirectories(dir);
        } catch (final IOException ex) {
            // Must NOT map to IOException - see
            // https://java.net/jira/browse/TRUEZIP-321 .
            throw new IllegalArgumentException(dir + " (cannot create directory for temporary files)",
                    ex);
        }
        assert exists(dir);
    }

    @Override
    public void release(Entry resource) throws IOException {
        resource.release();
    }

    /** A temp file pool entry. */
    @NotThreadSafe
    private static final class Buffer
    extends FileEntry implements Entry {

        Buffer(Path file, final TempFilePool pool) {
            super(file);
            assert null != file;
            assert null != pool;
            this.pool = pool;
        }

        @Override public void release() throws IOException { pool(null); }

        private void pool(final @CheckForNull TempFilePool newPool)
        throws IOException {
            final TempFilePool oldPool = this.pool;
            this.pool = newPool;
            if (oldPool != newPool) deleteIfExists(getPath());
        }

        @Override
        @SuppressWarnings("FinalizeDeclaration")
        protected void finalize() throws Throwable {
            try { pool(null); }
            finally { super.finalize(); }
        }
    } // Buffer
}